Method of manufacturing metal articles by electroforming



United States Patent U.S. o1. 204-9 3 Claims ABSTRACT OF THE DISCLOSUREMethod of making small diameter'thin walled tubing by electroplating ona metal wire mold having a high value of permanent elongation and thenremoving the mold by stretching the mold to reduce its diameter/Anexample of such a'wire mold is soft annealed coppenT his abstract is inno way intended to be a description of the invention defined by theclaims.

The invention in this case relates to a method of manufacturing metalobjects having channels of small diameter such as thin walled tubinghaving inner diameters of 1 mm. or less.

According to one method known in the art, such a metal object may beproduced by electrodepositing metal on a wax mould having a conductivesurface and then removing the wax mold by melting. However, this methodhas not proved too useful when employed for objects having smalldiameter channels since in such cases not only does the low rigidity ofthe mould constitute a problem but also the melting of the wax presentsa problem due to the capillary action of the deposited metal.

In another proposed method, the metal is deposited on a metal mould of achemically dissimilar metal which mold is removed by dissolving with aselectively acting reagent. However, this method has not proved toosuccessful because the small surface area of the mold presented to thereagent results in a low rate of dissolving and therefore a slowprocedure.

According to still another known method, metal is electrodeposited on amould formed of a material which when heated to a high temperature has arubber-like consistency and can be pulled out of the resultant outermetal shell. However, this method, which is described in German Patent1,090,481, suffers from the fact that the mould material is easilybroken thus causing broken pieces of mould material to remain in thechannel and tends to adhere to the metal because of its adhesivecharacter.

In the method of my invention, the above-noted difficulties of the priorart are eliminated or greatly reduced. According to my method, in orderto produce a metal object having a very narrow channel, metal iselectrodeposited on a thin metal wire mould formed of a metal having ahigh value of permanent elongation preferably of more than 20%, thenloading the wire mold above its tensile limit until it decreases indiameter and finally fractures and then pulling out the two pieces ofwire mould from the electrodeposited metal.

Soft-annealed metals such as soft annealed copper and aluminum wirehaving permanent elongations of about 30 to 40% are particularly usefulfor the wire moulds. Particular examples of such metals are disclosed inColin 1. Smithells Metals Reference Book, vol. 11, published 1955 byInterscience Publishers, Inc., New York. Aluminum and aluminum alloysthat may be employed are described in pages 714716. For example aluminummetals 3,472,741 Patented Oct. 14, 1969 ice and alloys (as designated inparentheses) of the following B.S./GE. specifications may be employed, SAO, E AM, S B-O, E B-M, SiCO, EiCM, NS O (Al-Mn), NS M (Al-Mg-Mn).Copper and copper alloy products that may be employed for the mould aredescribed on pages 727-732. Some examples identified by the B.S.specifications or otherwise are: O.F.M. copper strip-annealed, H.C.copper B.S. 1432 strip-annealed, silver bearing copper strip annealed,tellurium copper rodextruded, cap copper B.S. ST A. 17-strip-annealed,brass 70/30 B.S. 267-strip-annealed, nickel silver 10% B.S. 709 stripannealed. Other suitable materials such as nickel and nickel alloys,zinc and zinc alloys and steels are disclosed on pages 754, 755, 760,766, 767, 768 and 770 of this book.

Any metal that may be deposited by electrodeposition may be employed toform the metal object through which the channel is formed. Examples ofsuch metal are nickel, copper, silver, tin, gold, chromium, cadmium andzinc.

My invention will now be described in greater detail with reference tothe following example for the manufacture of nickel pipes having aninside diameter of 0.55 mm., an outside diameter of 1.1 mm. and a lengthof at least 15 mm.

Soft-annealed copper wire having a diameter of 0.55 mm. is stretched ona frame having a side of 300 mm. and then decreased cathodically for 30seconds at room temperature in an aqueous electrolyte solution whichcontains per litre:

30 g. of sodium carbonate, calculated as anhydrous,

30 g. of sodium cyanide,

30 g. of sodium silicate, and

30 g. of tertiary sodium phosphate (with a current density of 4 A./dm.

Then the cathode frame with the stretched wire is rinsed in water,dipped for a moment in an aqueous solution of hydrochloric acid (1:10)at room temperature, again rinsed in water, dipped in a solution of 20g. of potassium dichromate in water at room temperature for 5 seconds,again rinsed and then transferred to a nickel plating bath.

This bath has the following composition:

200 g. NiSO -7H O 2 g. sodium benzene disulphonic acid and water to 1litre.

The bath was heated to 50-55 C. and the copper wires nickel plated at acurrent density of 10 A./ sq. dm. for 2 /2 hours. The wires were thenrinsed in water and dried. The grown wires were cut off the sides of theframe and the nickel layer Was removed at the two extremities of theresulting pieces of wire. The copper wires were then elongated untilthey fractured. The pieces of copper wire were then pulled out leaving aresultant nickel pipe.

While I have described my invention in connection with specificembodiments and applications, other modifications thereof will bereadily apparent to those skilled in this art without departing from thespirit and scope of the invention as defined in the appended claims.

What I claim is:

1. A method of manufacturing metal objects containing channels or holesof small diameters comprising electrodepositing a desired metal on awire mould, said wire mould being formed of a metal having a high valueof permanent elongation of more than about 20%, loading said wire mouldbeyond its tensile limit to thereby reduce the diameter of said wiremould and cause it to fracture and then separating said wire mould fromthe electrodeposited metal.

2. The method of claim? wherein the wire mould is OTHER RIg ERENCES 2x53 25 5' d 2533 f fi s ggg i 2 3 331 2 i of Safranek, W. H., DOIltOverlook Electroforming, June 3. Metal objects having holes or channelssrnall di- 1961 Product Engmeenng 609414) ameter formed by the method ofclaim 1. 5 JOHN M ACK, primary Examiner R f es Cit d T. TUFARIELLO,Assistant Examiner FOREIGN PATENTS CL 153,231 10/1920 Great Britain.204-4

